A sick and moribund layer bird. Infectious coryza primarily affects replacement pullets and adult layers, not young broilers. Uncomplicated coryza rarely kills birds. When a layer becomes severely depressed, stops eating, and approaches death, this almost always indicates complications or co‑infections.

Avibacterium paragallinarum, the causative agent of infectious coryza, is associated with:

• A localised upper respiratory infection
• Producing sinusitis, conjunctivitis, nasal discharge, and reduced feed intake
• But not typically causing systemic disease or septicaemia